A little filming I did around our Rock Crusher this winter. Curious what everyone thinks of the filming quality, and what I need to work on when filming.

Looks pretty good to me.  One note of caution,  when flying close to large metal like that,  beware of the compass possibly freaking out.  You also may want to turn down the gains on the controller to smooth out control inputs.  It's all according to what your end goals are for the video.   Are you using an ND filter?  I ask because your exposure looks pretty good to my ( admittedly ) untrained eye.
I always wanted an excavator like that to play with,  and an ore crusher to see if there really is gold here.  

No on the lense, I did all the editing through iMovie. Our guy operating the crusher wasn't wanting to see a drone go down, so he was thankfully paying close attention also. He loved the video though.

It is a new theme but be aware of the magnetic field's influence like what kneepuck said above. Here are the safety tips:  https://www.youtube.com/playlist?list=PL8-vxWY64sBOmkQQJ2KWNL-uRBZsP43-r
What's more , don't forget to clean your drone after the dusty flight